Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems

Everett Shock, Thomas McCollom, Mitchell D. Schulte

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of redeuced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.

Original languageEnglish (US)
Pages (from-to)141-159
Number of pages19
JournalOrigins of Life and Evolution of the Biosphere
Volume25
Issue number1-3
DOIs
StatePublished - Jun 1995
Externally publishedYes

Fingerprint

chemical energy
hydrothermal systems
Seawater
hydrothermal system
hydrothermal fluid
seawater
fluids
energy
Oceans and Seas
Synthetic Chemistry Techniques
Gibbs free energy
Carbon Monoxide
Atmosphere
Thermodynamics
Sulfur
early Earth
pressure dependence
Polymers
oceans
fugacity

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Agricultural and Biological Sciences (miscellaneous)
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems. / Shock, Everett; McCollom, Thomas; Schulte, Mitchell D.

In: Origins of Life and Evolution of the Biosphere, Vol. 25, No. 1-3, 06.1995, p. 141-159.

Research output: Contribution to journalArticle

@article{6684cbc34da54d0590b18c2e1d2f87ff,
title = "Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems",
abstract = "Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of redeuced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.",
author = "Everett Shock and Thomas McCollom and Schulte, {Mitchell D.}",
year = "1995",
month = "6",
doi = "10.1007/BF01581579",
language = "English (US)",
volume = "25",
pages = "141--159",
journal = "Origins of Life and Evolution of Biospheres",
issn = "0169-6149",
publisher = "Springer Netherlands",
number = "1-3",

}

TY - JOUR

T1 - Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems

AU - Shock, Everett

AU - McCollom, Thomas

AU - Schulte, Mitchell D.

PY - 1995/6

Y1 - 1995/6

N2 - Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of redeuced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.

AB - Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of redeuced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.

UR - http://www.scopus.com/inward/record.url?scp=0028974644&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028974644&partnerID=8YFLogxK

U2 - 10.1007/BF01581579

DO - 10.1007/BF01581579

M3 - Article

C2 - 11536667

AN - SCOPUS:0028974644

VL - 25

SP - 141

EP - 159

JO - Origins of Life and Evolution of Biospheres

JF - Origins of Life and Evolution of Biospheres

SN - 0169-6149

IS - 1-3

ER -